Analog Devices Inc. AD7731BRUZ

Overview

AD7731BRUZ from Analog Devices is a 24-bit sigma-delta analog-to-digital converter optimized for high-precision industrial process control front ends. It features a programmable gain amplifier supporting seven unipolar (0 to +1.28 V) and seven bipolar (±1.28 V) input ranges, 16-bit peak-to-peak resolution at 800 Hz output rate, and integrated self/system calibration with <5 nV/°C offset drift. It operates from a single +5 V analog supply and interfaces via SPI-compatible 3-wire serial protocol.

For engineers reviewing the AD7731BRUZ datasheet, AD7731BRUZ pinout, AD7731BRUZ application, or AD7731BRUZ equivalent, this page delivers verified technical context, real-world timing and noise performance, calibrated accuracy specs across input ranges, FASTStep™ channel sequencing behavior, and RoHS-compliant TSSOP-24 packaging details - all directly traceable to Analog Devices' official AD7731 Rev. A documentation.

Technical Context

The AD7731BRUZ implements a two-stage digital filter: a programmable SINC³ modulator followed by either a 22-tap FIR filter (default) or FASTStep™ adaptive filter for rapid step-response settling. Its on-chip PGA provides gain settings enabling direct connection to low-level transducers (e.g., ±20 mV), while internal chopper stabilization reduces drift to 5 nV/°C in CHP = 1 mode.

It supports three buffered differential analog input pairs (configurable as five pseudo-differential channels), differential reference input (±2.5 V or ±5 V), and dual-function pins AIN3/D1 and AIN4/D0 that serve as programmable digital outputs when enabled. The device achieves 88 dB normal-mode 50/60 Hz rejection and 120 dB common-mode rejection on REF IN, critical for noisy industrial environments.

Key Specifications

Pinout & Package

AD7731BRUZ is housed in a 24-lead TSSOP package (RU-24), RoHS-compliant, with 0.65 mm lead pitch and exposed pad for thermal management. Pin 1 is located at top-left per standard JEDEC outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-precision sigma-delta ADC applications.

Compared with AD7730BRUZ and ADS1258IPWR, the AD7731BRUZ uniquely combines programmable differential/pseudo-differential input topology, on-chip burnout detection, FASTStep™-accelerated settling, and chopper-stabilized ultra-low drift - making it the only option qualified for demanding, multi-sensor industrial front ends requiring both diagnostic capability and metrological stability.

Availability

AD7731BRUZ is available at Aetrix Electronics and suitable for PLC analog input modules, industrial weigh scale controllers, DCS field instrument interfaces, and process analyzer signal conditioning requiring stable component supply across extended temperature and long product lifecycles.

Supply support for AD7731BRUZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Wilmington, MA.

The AD7731BRUZ belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for industrial process control front ends where transducer interface integrity, long-term drift stability, and built-in diagnostics are non-negotiable.

FAQ

What is the maximum output data rate supported by the AD7731BRUZ?

The AD7731BRUZ supports programmable output rates up to 6.4 kHz in SKIP mode, where only the SINC³ filter is active. In normal mode with both SINC³ and 22-tap FIR filtering enabled, the maximum rate is 800 Hz - delivering 16-bit peak-to-peak resolution. The device's FASTStep™ mode maintains 13-bit p-p resolution during 1-ms channel switching, making it optimal for multiplexed sensor acquisition. All timing is synchronized to the 4.9152 MHz master clock.

Does the AD7731BRUZ require an external reference voltage?

No, the AD7731BRUZ does not require an external reference - it accepts a differential reference input (REF IN[+] and REF IN[–]) that can be set to either +2.5 V or +5 V nominal via the HIREF bit in the Mode Register. The part includes reference detect circuitry that asserts the NO REF flag if the reference falls below 0.3 V, enabling robust fault monitoring. External references must meet the absolute voltage limits: AGND – 0.03 V to AVDD + 0.03 V.

How does the FASTStep™ mode improve channel switching performance in the AD7731BRUZ?

FASTStep™ mode in the AD7731BRUZ replaces the default 22-tap FIR filter with an adaptive filter upon detection of a step input change, reducing settling time from typical FIR settling (tens of milliseconds) to 1 ms while maintaining 13-bit peak-to-peak resolution. This is achieved by dynamically reconfiguring the second-stage digital filter path - confirmed in Figure 3 and page 29 of the AD7731 Rev. A datasheet - and is essential for high-speed multiplexed acquisition across AIN1–AIN6 without sacrificing accuracy.

Can the AD7731BRUZ operate with separate analog and digital supplies?

Yes, the AD7731BRUZ supports independent analog and digital supplies: AVDD = +5 V (±5%) for analog circuitry, and DVDD = +2.7 V to +5.25 V for digital I/O and logic. AGND and DGND are separate pins but must be tied together at a single point on the PCB to prevent ground loops. This separation minimizes digital switching noise coupling into sensitive analog paths - a key design requirement validated in the device's 110 dB PSR spec at low input ranges.

What is the purpose of the AIN3/D1 and AIN4/D0 pins on the AD7731BRUZ?

The AIN3/D1 and AIN4/D0 pins on the AD7731BRUZ are multifunctional: they operate as programmable-gain analog inputs by default, but can be reconfigured as digital output bits D1 and D0 via the DEN (Digital Enable) bit in the Mode Register. When enabled as outputs, their logic states are controlled by bits D1 and D0 in the same register - allowing the AD7731BRUZ to drive status LEDs, enable external circuitry, or synchronize auxiliary functions without requiring additional GPIOs from the host microcontroller.